Robot joint space point-to-point movement trajectory planning method

Abstract

A robot joint space point-to-point movement trajectory planning method. Joint space trajectory planning is performed according to the displacement of a robot from a start point to a target point during PTP movement and a limitation condition of a preset movement parameter physical quantity of each axis in a robot control system. An n-dimensional space is constructed by taking each axis of the robot as a vector, wherein n≥2, and the movement parameter physical quantity of each axis of the robot is verified according to a vector relationship between the n axes of the robot, so that a trajectory planning curve of each axis of the robot satisfies the limitation condition of the preset movement parameter physical quantity. The method has a small amount of calculations and strong real-time performance, the movement curves are mild, the control time is optimal, and the algorithm execution effect is good.

Description

FIELD OF THE INVENTION[0001]The invention relates to a trajectory planning method for a robot, and particularly to a trajectory planning method for point-to-point motion in robot joint space.BACKGROUND OF THE INVENTION[0002]With the development of modern technology, industrial robots have more and more applications, and the forms of working tasks in various application fields get more diversified as well. There are high requirements on real-time control in a robot application scenario such that a robot control system needs to provide an efficient motion control strategy. As a key technology in a robot control system, the trajectory planning of robot motion directly determines the operating efficiency of the control system and plays an important role in whether a robot can complete high-speed and high-precision machining.[0003]There are two kinds of motion trajectories commonly used by robots: linear and arc motion trajectories in Cartesian space; and point-to-point motion trajectori...

AI Technical Summary

Benefits of technology

[0008]Technical problems to be solved by the invention are as follows: for the problems of a large calculation amount and a longer planned trajectory running time in the trajectory planning of PTP motion of a robot in the prior art, the invention provides a trajectory planning method for point-to-point motion in robot joint space, wherein trajectory planning is performed on the joint space based on preset constraints on physical quantities of motion parameters of each axis in a robot control system as well as the displacement of a robot from a starting point to a target point during the PTP motion. The method of the invention has smaller calculation amount and meets the requirements on real-time performance in robot control. Moreover, the trajectory planning of the PTP motion of the robot by the method of the invention enables the robot to smoothly move at an optimal time, thus effectively ensuring the operating efficiency of the robot during working and greatly improving the motion tempo of the robot in an actual working task.

[0021]Since the motion curve of each axis of the robot is obtained by projecting a motion trajectory of the generalized virtual axis, the change trend of the motion curve of each axis is consistent with that of the motion curve of the generalized virtual axis. When the generalized virtual axis performs accelerated or decelerated motion, the curve decomposed onto each axis is also in an accelerated or decelerated motion process; and when the generalized virtual axis performs uniform motion, the curve decomposed onto each axis is also in a uniform motion process. The motion curves of all axes of the robot have a consistent change trend, which enables the robot to have smooth motion trajectories and the system to be stressed without impact. Moreover, a trajectory planning curve of each axis of the robot satisfies its preset constraints on the physical quantities of the motion parameters after projection; and all axes can be started simultaneously and stopped simultaneously when each axis runs based on its trajectory planning curve. The verification by back projection using the n-dimensional space projection method in the trajectory planning of the generalized virtual axis allows that the execution time of the PTP motion of the robot is optimal, and at least one axis reaches its maximum running capability during motion, thus effectively ensuring the operating efficiency of the robot.

[0022]The trajectory planning method for point-to-point motion of a robot according to the invention can satisfy the application requirements on synchronous operation of all axes of the robot during the PTP motion. Separated trajectory planning for each axis is avoided during the selection of a reference axis, thus reducing the number of trajectory planning in the PTP motion of the robot. Compared with a conventional method, the method of the invention has a small calculation amount, can be highly achieved in the control system, and meets the requirements on real-time performance in robot control. In the method of the invention, trajectory planning is performed on the generalized virtual axis and the motion parameters of each axis are verified by the n-dimensional space projection method such that the planned motion curves of all axes have a consistent change trend, and the acceleration and deceleration process of each axis is synchronous with that of other axes. In the multi-axis composite motion process of the robot, the entire system is stressed without impact and abrupt change, the robot has smooth motion trajectories, and moving parts have low loss. The trajectories of the robot planned during the PTP motion by the method of the invention are not beyond the preset constraints on the physical quantities of the motion parameters of each axis, and allow all axes to reach the maximum moving capability as much as possible within an allowable range of parameters. The trajectory planning method of the invention enables the robot to operate at an optimal time, thus effectively ensuring the operating efficiency of the robot during working and greatly improving the motion tempo of the robot in an actual working task. The trajectory planning method for point-to-point motion in robot joint space provided by the invention is characterized by strong real-time performance, a soft motion curve, an optimal control time and a good algorithm execution effect, and therefore suitable for field applications of industrial robots.

Problems solved by technology

Robots generally have multiple axes, and a PTP motion using the above method requires multiple trajectory planning with a huge calculation amount such that trajectory points may not be generated in a control cycle during the real-time planning in robot control, thus failing to meet the requirements on real-time control.

Therefore, the motion time selected by the method of the patent is not necessarily an optimal time for the PTP motion, and it may take a longer time to complete a PTP motion, thus affecting the efficiency of the robot in actual machining.

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